This invention relates to a method for fabricating an optical attenuator by fusion splicing of optical fibers and more particularly by using surface tension that occurs during fusion to align the previously offset cores of the fibers.
In an undersea lightwave transmission system, it is desired to have the same optical loss in all fibers of the cable between each pair of repeaters. Because there likely is a different loss in each different fiber, an optical attenuator is inserted in line with the fiber as a lumped buildout loss in the low loss ones of the fibers.
In the prior art, optical attenuators are provided as separate piece parts which are inserted between the ends of two optical fibers by means of mechanical coupling devices. Inserting such an optical attenuator into a system adds not only the attenuator itself but also the mechanical coupling devices. It is well known that system reliability is reduced by any increase in the number of separate components, or devices, used in the system. Thus the insertion of the optical attenuator plus the coupling devices not only increases optical loss but also reduces system reliability.
For an undersea optical fiber transmission system requiring very high reliability, it is desirable to insert an optical attenuator between the ends of two optical fibers by using the lowest possible number of separate parts to retain high reliability while increasing optical loss. Thus there is a problem finding a way to insert an optical attenuator between the ends of two optical fibers without reducing reliability.